Enable proper testing of matrix-scalar ops.

Now that the various Metal and SPIR-V bugs have been shaken out, we can
enable these tests. Knock on wood.

Change-Id: If4b4e302cfdd91464aaf00bc9639989de5e49aac
Bug: skia:11985
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/408640
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
9 files changed